Patent Document 1 discloses an insulated wire that includes a core wire and an insulating covering that covers the outer surface of the core wire while exposing an end portion of the core wire, wherein a leading end portion of the end portion is formed with the shape of a terminal connection portion that can come into direct contact with and be connected to a partner terminal with which a connection is to be made. In Patent Document 1, the core wire is formed by multiple strands, and the leading end portion is formed with the shape of the terminal connection portion by welding of the strands.